[Python-checkins] cpython: Issue #20208: Clarify some things in the Python porting HOWTO.
brett.cannon
python-checkins at python.org
Fri Jan 17 17:45:11 CET 2014
http://hg.python.org/cpython/rev/863b8e71cfee
changeset: 88523:863b8e71cfee
user: Brett Cannon <brett at python.org>
date: Fri Jan 17 11:45:01 2014 -0500
summary:
Issue #20208: Clarify some things in the Python porting HOWTO.
Thanks to Rodrigo Bernardo Pimentel, Ondřej Čertík, and Dmitry
Shachnev for the feedback leading to the changes.
files:
Doc/howto/pyporting.rst | 20 +++++++++++---------
1 files changed, 11 insertions(+), 9 deletions(-)
diff --git a/Doc/howto/pyporting.rst b/Doc/howto/pyporting.rst
--- a/Doc/howto/pyporting.rst
+++ b/Doc/howto/pyporting.rst
@@ -151,15 +151,17 @@
``from __future__ import unicode_literals``
'''''''''''''''''''''''''''''''''''''''''''
-If you choose not to use this future statement you should then mark all of your
+If you choose to use this future statement then all string literals in
+Python 2 will be assumed to be Unicode (as is already the case in Python 3).
+If you choose not to use this future statement then you should mark all of your
text strings with a ``u`` prefix and only support Python 3.3 or newer. But you
are **strongly** advised to do one or the other (six_ provides a function in
case you don't want to use the future statement **and** you want to support
Python 3.2 or older).
-Bytes literals
-''''''''''''''
+Bytes/string literals
+'''''''''''''''''''''
This is a **very** important one. Prefix Python 2 strings that
are meant to contain bytes with a ``b`` prefix to very clearly delineate
@@ -504,12 +506,13 @@
Update ``map`` for imbalanced input sequences
'''''''''''''''''''''''''''''''''''''''''''''
-With Python 2, ``map`` would pad input sequences of unequal length with
-`None` values, returning a sequence as long as the longest input sequence.
+With Python 2, when ``map`` was given more than one input sequence it would pad
+the shorter sequences with `None` values, returning a sequence as long as the
+longest input sequence.
With Python 3, if the input sequences to ``map`` are of unequal length, ``map``
will stop at the termination of the shortest of the sequences. For full
-compatibility with ``map`` from Python 2.x, also wrap the sequences in
+compatibility with ``map`` from Python 2.x, wrap the sequence arguments in
:func:`itertools.zip_longest`, e.g. ``map(func, *sequences)`` becomes
``list(map(func, itertools.zip_longest(*sequences)))``.
@@ -518,9 +521,8 @@
When you run your application's test suite, run it using the ``-3`` flag passed
to Python. This will cause various warnings to be raised during execution about
-things that 2to3 cannot handle automatically (e.g., modules that have been
-removed). Try to eliminate those warnings to make your code even more portable
-to Python 3.
+things that are semantic changes between Python 2 and 3. Try to eliminate those
+warnings to make your code even more portable to Python 3.
Alternative Approaches
--
Repository URL: http://hg.python.org/cpython
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